R help - Jan 2005 - S4 class no longer accepts matrix in array slot under 2.0.1

I have an S4 class with a slot of class "array", and in upgrading to
2.0.1
(from 1.9.1) I have encountered a change in behaviour. This causes me some
difficulties if I want to allow 2-dimensional arrays in the slot.

The following (in 2.0.1) illustrates the point:
> setClass("foo",representation("array"))
[1] "foo"
> a <- new("foo",array(NA,2:4))
> b <- new("foo",matrix(NA,2,3))
Error in "as<-"(`*tmp*`, Classi, value = c(NA, NA, NA, NA, NA, NA))
:
        No method or default for as() replacement of "foo" with
Class="matrix"

This last error did not occur under 1.9.1.

I conclude that in this context the methods package does not recognise
"matrix" as a subclass of "array". However if I use
getClass(), I see that R
recognises "matrix" as a subclass of "array" (and
vice-versa).  So is this
new behaviour correct?

[this is a simplified (and final) reposting of an earlier question entitled
"matrix no longer "is" array in 2.0.1?"]

Giles Heywood wrote:
>I have an S4 class with a slot of class "array", and in upgrading
to 2.0.1
>(from 1.9.1) I have encountered a change in behaviour. This causes me some
>difficulties if I want to allow 2-dimensional arrays in the slot.
>
>The following (in 2.0.1) illustrates the point:
>
>  
>
>>setClass("foo",representation("array"))
>>    
>>
>[1] "foo"
>  
>
>>a <- new("foo",array(NA,2:4))
>>b <- new("foo",matrix(NA,2,3))
>>    
>>
>Error in "as<-"(`*tmp*`, Classi, value = c(NA, NA, NA, NA, NA,
NA)) :
>        No method or default for as() replacement of "foo" with
>Class="matrix"
>
>This last error did not occur under 1.9.1.
>
>I conclude that in this context the methods package does not recognise
>"matrix" as a subclass of "array". However if I use
getClass(), I see that R
>recognises "matrix" as a subclass of "array" (and
vice-versa).  So is this
>new behaviour correct?
>
>[this is a simplified (and final) reposting of an earlier question entitled
>"matrix no longer "is" array in 2.0.1?"]
>
>  
>
Hi,

 > setClass("foo",representation("matrix"))
[1] "foo"
 > a <- new("foo",array(NA,2:4))
 > b <- new("foo",matrix(NA,2,3))
 >
Will work.
As you say array has a subclass matrix.

getClass("array")
....
Known Subclasses: "matrix"

and

getClass("matrix")
Known Subclasses:
Class "array", directly, with explicit test and coerce

and matrix has a subclass array.

What probably is necessary to use polymorphism -> assigning a subclass 
to the parent class is the "explicit test and coearce".
It seems that matrix is the superclass of array.

/E
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>  
>



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